Montage amplifier



Marh 4, 1958 A. J. BARACKgET 2,325,755

MONTAGE AMPLIFIER Fi l ed March 28, 1952 4 Sheets-Sheet 1 ELECTRONICKEYER AUTO SWITCHWG INVENTQR ALBERT J. BARACKET ATTORNEY MaIII--4, 1958.Filed March 28, 1952 A. J. BARACKET MONTAGE AMPLIFIER LINE LINEI LINE nLIHE n+1 LINE 262.5

LINE I LINE n LINE 1n+I l5 LINE 262.5 v

LINEI LINE n UNE 11+| LINEI LINE n LINE max LINE n- -b LINE 262.5

MASKED SLIDES LINE 262.5

{SCANNING FIELD- 4 Sheets-Sheet 2 LINES Ho 2625 LINES [T071 1% i I: \w IIsb I8 umzs lTon LINES min 262.5

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25 4LINES -n+b O DERIVED PULSES INVENTOR ALBERT J. BARACKET BY air ORNEY March 4, 1958 A. J. BARACKET 2,32

MONTAGE AMPLIFIER Filed March 28. 1952 Sheets-Sheet 3 fa fl A I VIDEOcoMMoN 45 VlDEO CHANNELA vmzo CHANNELB f I mVENToR 'ALBERT d BARACKETATTORNEY/ March 4, 1958 A. J. BARACKET MONTAGE AMPLIFIER Filed March 28,1952 4 Sheets-Sheet IFOOFBSW INVENTOR ALBERT J. BARACKET ATTORNEY UnitedStates Patent 6 MONTAGE AMPLIFIER Albert J. Baracket, Bloomfield, N..l., assignor to International Telephone and Telegraph Corporation, acorporation of Maryland Application March 28, 1952, Serial No. 279,230

6 Claims. (Cl. 178-7.1)

This invention relates to electronic amplifier systems and moreparticularly to a montage amplifier system incorporated in a televisionor similar broadcast system.

There are many situations where it would be advantageous to show twoscenes as though from separate picture pick-up units at one time on atelevision screen, or to show separated parts or separate views of thesame scene at the same time to focus the attention of the audience onthese separate segments. Another advantage of such a system would be toshow more distinctly two or more separate actions that blend to make acomplete picture of the players at widely separated areas in a game asin baseball and football, or enable the audience to observe two or moredistinct segments or views of the same action, or to include anadvertising announcement as a part of the picture. In televisiontransmission systems heretofore proposed, such operations wereaccomplished by superimposing two video frame signals which resulted inan overall reduction of contrast and brightness or both. It is an objectof this invention, therefore, to not only provide means forsimultaneously transmitting two or more separate TV video frame signalsfor presentation on a receiving TV screen in the same frame, but to sotransmit such signals that each of the separate video flame signals arepresented simultaneously with substantially the same contrast andbrightness as when they are presented separately.

Another object of this invention is the provision on the studio mastercontrol equipment of means for lap dissolving two separate and distinctvideo signals by fading one of the signals and bringing the other signalto a predetermined brightness to effect this overlap of signals.

' Still another object of this invention is the provision whereby theoperator of the studio or master control unit may select desired videosignals for presentation from one of several picture pick-up units.

A feature of this invention is the derivation of a keying pulse toeffect the simultaneous showing, for example, of two video frame signalsin the same frame. This keying pulse may be derived from one of thepicture pick-up projection units wherein is incorporated a systemcomprising a cathode ray electron discharge device emitting a lightsource developed from horizontal line scanning, a focusing lens, anopaque-transparent slide being scanned by the cathode ray device, acondensing lens, and a photo tube to respond to the presence of thescanning light passing through the opaque-transparent slide. The spacedivision of the opaque-transparent slide determines the time relation ofthe two video frame signals being presented simultaneously in one frameof a television presentation.

Another feature of this invention is a biasing system controlled fromthe panel of the studio equigpment wherein the fading out of one videosignal and the bringing up to brightness of another video signal may beselectively controlled at different rates.

Still another feature of this invention is the switching arrangementwhich allows the master control operator to ice 2 select either of twovideo signals, the lap dissolving of two video signals, the fading outand bringing up to brightness of two video signals, or the presentationof two video signals simultaneously in the same frame of a TVpresentation.

The above-mentioned and other features and objects of this inventionwill become more apparent by reference to the following descriptiontaken in conjunction with the accompanying drawings, in which:

Figs. 1 and 1A show a schematic and block diagram of the control systemand its association with the units of a montage system following theprinciples of this invention;

Fig. 2 illustrates representative space arrangements of the specialopaque-transparent slides that may be employed with the keying pulsederiving circuit and the corresponding keying pulses produced therefrom;

Fig. 2A illustrates a modified form of slide to effect by movementthereof a variation in the time division between two video frame signaisdesired for a single frame;

Fig. 3 is a schematic diagram of the montage amplifier of Fig. l; and

Figs. 4 and 5 illustrate a multivibrator type circuit and asawtooth-diode pick-off circuit, respectively, for application as theelectronic keyer of Fig. 1. Referring to Figs. 1 and 1A, alignmenttherebetween established by conductors 4d and 41, there is illustrated amontage system or a master control arrangement which includes thereinthe montage amplifier 1, picture pick-up units 2 and 3, remote picturepick-up units 4 and 5, the controlling relays and switches, and thechannel pre-selector 6 necessary to achieve the features and objects ofthis invention. Adjacent to or included in one of the pick-up units, forthis example pick-up unit 3, is the means for deriving a keying pulsewhich comprises an electron discharge device of the cathode ray type 7wherein horizontal and vertical scanning produces a source of light, afocusing or condensing lens 8, one of a number of special slides 9, orcards at the face of cathode ray device 7, a light collector 10, and aphoto tube 11 with its accompanying circuit across which a pulse shapedvoltage is produced corresponding in a time relation with the spacerelation of the opaque and transparent segments contained in each slideor picture frame card.

The slide or card is the major element of the means for deriving thekeying pulse. The spacing of the opaque and transparent segments may bevaried to suit a predetermined arrangement of video signals in oneframe, this predetermined arrangement producing a keying pulse whichcuts on and off the proper video channel to establish the predeterminedarrangement of video signals in the single frame of the TV presentation.

Several arrangements of the opaque and transparent segments of the slideor card and the pulses produced by the horizontal line scanning of thesesegments are shown in Fig. 2 compared to a completely transparent slideor card 12 and the keying pulse 13 derived therefrom. The pulse 13represented therein is identical for each line of scanning and indicatesequal light intensity as the line of light scans or traverses the entirewidth of the slide. The masking or picture frame dividing of atransparent slide produces an opaque-transparent slide, examples ofwhich are shown at ?a, 95;, 9c, and 9d, Fig. 2, wherein the segment 14is transparent and the segment 15 is opaque.

Line scanning of slides as herein shown, or any other.

frame division, or combinations thereof, produces voltage pulses havinga positive sense when the scanning line is in the opaque portion and anegative or less positive sense when the scanning line is in thetransparent portion. The

. pulses derived therefrom are acted on by the keyer channel of themontage amplifier 1, Fig. 3, to present the input V lieyer pulse tovideo channel A and an inverted input pulse,

Patented Mar. 4, 1958 to channel B. Therefore,

the action of a positive pulse presented to the keyer channel would beto key on channel A and key olf channel B for the duration of the pulse,or series of pulsesas the ease may be, allowing the passage ofsignalspresentedto channel A, whilea negativepulse P od y an Opaqu po key-L ftchannel A and key on chan nel B providing a time sharing of the signalframe or output spectrum between selectedvideo signal sources asestablished by the divisionjof the slide or picture frame. Flexibilityis provided herein to reverse the keying of the channels as hereabovedescribed.

Slide 9a, Fig. 2, produces two pulses 16 and 17,de pendentnpon thelocation of the scanning line. As shown, a pulse 16 having a positivesense is produced by the scanninglines 1 to it, while a pulse 17, havinga negative sense is produced by the scanning lines n+1 to 262.5. Slidesor picture frames 9b, 9c, and 9d illustrate arrangements of the slideswherein the full width need not be masked. Accordingly, keying pulsesare derived substantially as indicated in Fig. 2, the circuitry employedin the montage amplifier 1 having a response fast enough tosubstantially follow the changes therein noted. Slide 91; develops apulse 18 containing both positive and negative sense pulses 18a and 18b,respectively, by scanning lines l to n to provide time sharing in thisportion of the signal frame while the remaining portion 'of the pictureframe produces a positive sense pulse 19, the overall result providing atime sharing of the, signal frame between two selected videosignalsources. Slide 90 develops a pulse 2i having the negative sensepulse 20:: in the center thereof bounded by the positive sense pulses2%, corresponding to the masked portion of the slide, by scanning lines1 to n, the remaining portion of the picture frame producing a positivesense pulse 21. Slide 92d develops a pulse 22 havinga positive sense.between line 1 and lin'e n, and a-series of pulses 23 and 24.;betweenlinen and line 262.5 having negative sense pulse 25 with an increasingtime duration corresponding to the increasing width of the masked oropaque portion 14. It will be apparent that the positive pulses 16, 19,21, and 22 are substantially identical to the pulse 13 produced by theopaque slide and associated scanning lines.

Following the principles herein set down, production of keying pulses.and their proper relationship to the masked slides may be developed forany arrangement of masking or combinations thereof. Anothervariation inthe slides, 92, Fig. 2A, provides for employmentof a picture frameandhaving a length longer thanthe aetual proportional frame dimensionsand a variable, line 01 demarcation between the opaque and transparentpor tions'14 and 15 whereby the time sharing of two video signals inthesignal frame may be varied. This variable timesharing is accomplished bysliding this picture frame card at a predetermined rate across thescanning field of the light beam. Efiicient operation of the circuitryto be-described can be augmented by the useiof clamp circuits at thecontrol and suppressor grids of devices 61 and'62 or byD.- C. couplingto these grids; The switches and controlling relays are shown in detailin'Figs.1 and 1A wherein the respective switches and relays are thevideo pushbutton selectors 30, 31, and l2, nonnal-rnontage switch 36,relays 37 and 47 and their associated contacts37a, 37b, and 47a, 47b,respectively, auto switching 39, and; fade rate switch 38, showing indetail the four sections 38a, 38b, 38c, 38d, incorporated therein. Alsoindicated are the video control potentiometers 32, 33, 34, 35 and theauxiliary video potentiometers 32a and 35a which control the bias andoutput voltage of the video signal sources 2 5,. 4, 3 respectively.

"-With switch 36, 'Fig. l in the normal orfNfposition,-relay-37 isinactivated establishinga; direct eonnectionfrom the video sources 2, 3,fl, and to their corresponding double throw or tlnnblerswitchesl, 27,28,.and 29, as shown. -These doublethrow switches provideto operator anopportunity to pass any one of the video signals through the channelpreselector 6 to either channel A or B of the montage amplifier 1,depending upon the position of switches 26, 27, 2 8, or 29. While asignal, from say video source '2, is passing through channel A ofmontage amplifier 1, as established by switch 26 being in position A andpushbutton 30 being depressed as indicated, the operator may prepare topresent another signal, from say video source 4, by-placing switch 28 inposition B. When the operator is prepared to present this second signal,he depressespushbutton 3 1, inactivat ing channel A andactivatingchannel-B for presentation of the second or pre-set signal to the signalframe. The change over from one video signal .to the other bypushbuttons 30 and 31 is accomplishedby fading the signal presentcompletely out andbring-ing-the' selected signal up to full brightnessat three different rates provided by the settings of the foursectioned-ganged fade rate switch 3 (8g, 33b, 38c, and 38d) .and theautoswitch 39. Switch '39 provides aconnection between a. negative po -itential source and the fade rate switch 38 establishing, the prqperOperating bias, in, either -lap'" or fade position', es nces, on thechannel amplifiers of the montage amplifier 1 through conductors 40 and41. Depressing pushbutton 42 establishes asubstantially equal bias forpre sentation to boththe channel I viding' the operator with a means tomanually lap dis solve two video signals selected from any of the fourvideo signal sources with switch 39 in the lap position. This manual lapdissolving process being accom plishedby manipulation of theexternalvideo control petentiometers '32, 33,. 34, and 35, respectively, videoselection being accomplished by switches 26, 27, 28, and

29, as hereinabove described. Employment of a pushbutton (l2 and switch39 in the fade position provides;

the operator with the opportunity to manually"accomplish superimpositionof two selected video signals.

The channel pre-selector 6 hereinabove mentioned pro-j vides a mixingfunction whereby eight possible signal inputs are combined for lowerswherein the cathode followers have their cath;

odes paralleled in groups of four, the output from each group beingpresented to their respective channels through terminals 43 and 44. Theinputsignals are applied to the controlgrids of the cathode followers inthe proper group to cooperate with switches 26, 27, 28, 29 andpushbnttonsjfl and 31 for the selection of a specified video signal tobe passed through the desired montage m ifi y hann Itis possible withmanual operation,

as selected pushbutton v42, to combine a plurality of,

i e si nal f m mined manner by 1 that all or any of these signals Iwill.bepresent in the signal sources 2, 3, v4, and 5 in a predeter ra e attt l vid 'Qutp t. ermiq l h P masist of; superimposition;

tion in thetsignal frame mayic of two video signals with" a d signalbeing lap dis,-

at the same time vde'a5:,tivati ng the v de e e sp ls n i a lo awar esssharing of a single signaliframe hy two video signals selected frompickup unit 2,v

s u es or ideo spurg el on ott eisits pints bmsPrq -id d b s iqhefli 28or .29 as. desired. The'p'ush button controls 30, 3 1, and 42, are

nede n r rat rs pe? i; sible,

and locked in .ipositi n w t e ein-e tail n asters-I eana V brightnessandcontra'st being controlled by the n monta amplifiers, therebypropassage through the two channel amplifiers by the montageamplifier 1. The circuitryinvolved in the pre-selector 6 includes eightcathode folpotentiometers 32, 33, 34,, and 35 so 't h respect .to thesetwo signals, superimposition he th rd leis-ha l .Q ny des ed om-v m seope t qn s .r elested by s t 36,. .QnqraiedT i fi h pla e keye pu se puel terminal 46 and, o #4 output. The

s eaves biases established by the circuitry of switch 38. Employing thetype of montage system herein described, wherein there is a time sharingbetween selected video signals for presentation in a single signalframe, provides a maintenance of picture contrast in both segments ofthe shared signal frame enjoyed by a single video signal in a signalframe. Therefore, when in montage operation, there is no decrease incontrast or brightness of the TV presentation.

As shown, the controls are set for normal operation by switch 36, andvideo channel A is selected to present its information with the gangedfade rate switches 38 set at fast and the auto switch 39 set at the fadeposition. These settings on the latter two switches provide for fastinterchange between channel A and channel B signals if the channel Bsignal is selected by pushbutton 31. With the operating condition asestablished by switch 36, relay 37 is inoperative allowing the videosignal from pick-up unit 3 to traverse channel A or B, depending uponthe setting of switch 27, and the keyer channel input 46 is grounded orotherwise shorted.

Operating normally with video signal A selected for TV presentation fromany selected video source, relay 48 is made operative by depressingpushbutton 30. Contact 48a assures that the activating voltage ismaintained across relay 48 to hold the remaining contacts in positionwhen pushbutton 30 is released. Contact 48b places a ground at point 49to produce the proper bias for the channels contained in the montageamplifier 1 through conductors 40 and 41 which provides the properoperating bias for channel A and inactivating bias for channel B, and toassure proper fading out of signal on channel A if channel B should beselected.

With the selection of channel A, the application of a ground at point 49provides that section b of switch 38 present a more positive voltagethrough conductor 41 to terminal 50 which allows video channel A tooperate. The network consisting of sections and d of switch 38, theresistive network 51 of the auto switch 39, and the negative bias atterminal 52 provides a voltage divider of such a relation that anegative bias is passed through conductor 40 to terminal 53, and henceto video channel B, rendering it inoperative. If channel B is selected,the polarity of the bias voltages applied to terminals and 53substantially reverse, making the now operative channel inoperative andso forth. However, it is not an instantaneous reversal of polarity but arate of reversal which will be discussed further in connection with Fig.3, allowing the channel A presentation to fade out and channel Bpresentation to come up to full brightness after channel A signal hascompletely faded out, the rate of change being controlled by the settingof switch 33 and the value of the RC time constants employed therein. Inselecting channel B, relay 4% is made inoperative and relay 54 isactivated producing the reversal of polarity in conductors 4i and 41 bymaking the necessary circuit changes in the controlling circuit,substantially as indicated hereabove in connection with channel A.

While the system is operating normally, the operator of master controlmay desire to overlap or superimpose two TV signals in the same frame.To accomplish this, the pushbutton 42 is operated which clears previouspushbutton settings by activating relay 47 and activates relay 55. Asmentioned in connection with contact 48a of relay 48, contact 55aprovides a holding means for relay 55 when the pushbutton 42 isreleased. Contact 55b of relay 55 places a ground at point 49 whilecontact 550 places a ground at point 59 providing a means forestablishing a more positive bias at both terminals 56 and 53 when theauto switch 39 is set at the lap or fade position. The contrast of theoverlapped signals, or the fading of two signals with respect to eachother, or the fading of one signal with respect to the overlappedsignals may be controlled manually by potentiometers 32, 33, 34, and 35dependent upon video signals selected by switches 26, 27,

6 28, and 29. The biasing to accomplish overlapping and fading as hereindescribed and for establishment of channel bias in montage operation maybe accomplished by employing the proper negative voltage source atterminal 52, such as volts, and the proper values of resistors containedthroughout the controlling circuit in connection with switches 33 and39, plus an RC time constant present in each of the channels to bediscussed hereinbelow. The value of these various components will dependupon the requirements established for a particular application.

N ow changing from normal operation to montage operation by a flip ofswitch 36, relay 37 is energized allowing the simultaneous presentationof two video signals in a time relation dependent upon the spacefunction of the selected slide, examples of which are shown in Figs. 2and 2A. The operation of switch 36 to the montage position inactivatesthe previously discussed controls by removing the rectified oractivating A.-C. from one side of the relays 48, 54, and 55 althoughpushbuttons are mechanically locked in position. When switching tomontage operation, the pushbutton conditions, as may be established whenswitch 36 is in the normal position, are not disturbed. For instance,when switching back to normal position after the montage operation, theprogram previously on is resumed instantaneously without furtheroperation of the pushbuttons 30, 31, and 32. Furthermore, while inmontage operation it is possible to operate the switches 26, 27, 28, or29 to change the video signals being montaged by the montage amplifier1.

The controlling circuit includes the lamps 480, 54a, and 55d forillumination of the pushbuttons 30, 31, and 32, respectively, when thesepushbuttons are depressed while switch 36 is in the normal position.When switch 36 is placed in the montage position, both lamps 43c and 54aare illuminated to give the operator an indication that both channels Aand B are in use. Lamps 30a and 31a are so located in the assembledapparatus that when they light up the operator will have a visualindication of which pick-up unit is supplying video signal to themontage amplifier in either normal or montage operation.

Operation of relay 37 removes contacts 37a and 37b from the indicatedposition to the other position, removing video #4 output from the inputto channel pre-selector 6. At the same time keyer terminal 46 isungrounded and the time function keying pulse is applied thereto frompick-up unit 3 and its associated pulse deriving circuit as hereinabovedescribed.

Referring to Fig. 3, a schematic diagram of the montage amplifier 1 isillustrated consisting principally of two wide band amplifier channelswhich may accept any pair of TV video signals, a common output device,and a keyer channel to accept a timing or keying signal from one 2f theabove-mentioned pick-up units, shown herein to be pick-up unit 3, thetime function dependent upon the space function of any one of a numberof selected slides which may be masked in a predetermined manner to beopaque in some sections and transparent in others, examples of which areshown in Figs. 2 and 2A.

The embodiment herein illustrated employs two wide band amplifiers 61and 62, one in each channel, which when the system is in montageoperation are keyed on and off by a keying pulse passed through thekeyer amplifier 63 which elevates the keying voltage to a levelsufficient to provide the desired keying on and off of the twoamplifiers 61 and 62. When a positive-going voltage is applied to thegrid 64 of amplifier 63, the current therethrough is increased causingthe voltage at the plate 65 to decrease. This decreasing voltage iscoupled through condenser 66 to the grid 67 of the amplifier 63 causinga decrease of current flow therethrough which in turn produces apositively-going or increasing voltage, amplified with respect to theincoming positive pulse. The increasing voltage is applied to the grid68 of the keyer driver electron device 69, causing a negatively-goingvoltage to appear at the plate 70 and a positively-going voltage toappear at the cathode 71. Voltage pulses are shown for the leads toplate 70 and cathode 71 includingboth positiveand negative-goingvoltages, indicating a 180 phase shift in one of these pulses ascompared to the pulse applied at terminal 46. This pulse applied to terminal 46 may be derived from a card substantially as shown in 9a of Fig.2. The voltage at plate'76 is applied to the suppressor grid '72 of thechannel amplifier 62 while the voltage at cathode 71 is applied to thesuppressor grid 73 of the channel amplifier 61 when the reversing switch74 is in its normal position as shown. The application of these voltagesfrom the electron device 69 will turn channel A on and channel B oil ina manner and for the proper duration dependent upon the selected slide 9employed to derive the keying pulse. When the keying pulse becomes anegatively-going pulse, the voltages are reversed at grids 72 and 73,keying 'ofi channel A and keying on channel 13. The grids 72 and 73 are"assured of receiving pulse shaped voltages of the proper amplitude dueto the cooperation of the D.-C. restorer or clamping circuit comprisingelectron discharge devices '75 and 76, respectively.

The resultant signal from both amplifiers 6i and 62 is applied to thecommon output electron discharge device 77, through an inductance 78 anda condenser79, 'onthe grids 80 and 81 in parallel. This common outputdevice 77 presents a combined frame portion of the signals of selectedvideo signal sources for transmission in the same signal frame at theterminal 45 from the cathode 83. The signal frame consists 'of each ofthe two'video input signals arranged in accordance with the spacedrelation of the opaque and the transparent sections of the special orselected slide 9 of Fig. 1, examples of which are shown in Figs. 2 and2A.

Composite synchronizing pulses from a synchronizing pulse source areconducted to terminal 34 of themontage amplifier 1, having a negativesense. These synchronizing pulses are amplified by electron dischargedevice 85 wherein the negative synchronizing pulse applied to the grid86 causes a positive pulse at the plate 87 which is coupled to the grid88 producing an amplified negative pulse-atthe plate 89. The voltage atplate 89 is coupled to the grid 99 of the keyerdriver 69, this sectionofwhich provides a reference bias and a means for applying the amplifiedsynchronizing pulses to clamp the signal level at various points in themontage amplifier circuit. From the plate 91 and the cathode 92, apositive and negative voltage, respectively, are applied to the clampingdevice 93 for clamping of the video signal at the grid 89 of the commonoutput device 77 at a desired predetermined level. The same thingmay beaccomplished at grid '64 of keyeramplifier63 by removing a positivevoltage from point94 and a negative voltage-from point-95 and applyingthese voltages to the clamp tube -96 and hence to clamp the keying pulseat grid :64. These two clamping operations assure that the variouspulses orsignals start froma certain predeterminedlevel prior toactivating their associated circuitry, thus presenting the propervoltage level at the output terminal 45 for transmission andsimultaneously producing a synchronizing influence on the montageamplifier.

The changes occurring in the control circuits of Figs. 1

and 1A by operation .of the .pushbuttons 33 and fi-lin conjunction withthe fade rate switch 38 and the auto switch 39 have beenfullyxdiscussedhereinabove. However, it was mentioned that the fadingoutand bringing up to brightness of the 't-wo signals was not aninstantaneous occurrence but was accomplished at-a'predetermined rate.Thefading rate,.-as it.is herein referredto, isestablished by the doubletime constant comprisingthe selected resistors'onith'esswitch 38und d-1econdensers 97, 93 .in conjunction with the resistors 99, 10 3 andcondensers 161, 102, :the formerltirne constants being shown in "Fig. 1and the latter' in Fig. 3. The value of thesetime-constauts1which:come.into play tor control of the video channelshythe selection of the master control operator are determined by theparticular application and results desired therein.

Switch 103, shown in Fig. 1, provides a means for selecting an alternatekeying pulse or control signal source. Thus an all-electronic system maybe provided by incorporating as the control signal source the electronickeyer 104. The circuitry incorporated therein may be any source of sparepulses whose time ratio of positive and negative portions may be varied.Figs. 4 and 5 indicate two alternate systems that may be incorporatedtherein to provide-a time sharing between two video signalssubstantiallyas described above in connection with the optical system incorporatingthe masked cards.

Fig. .4 indicates a variable multivibrator which is triggered from thesyncgenerator. The time constants incorporated in such a multivibratorcircuit are made variable to produce a keying pulse 106 whose positiveleading edge 197 is time varied by these variable time constants. Thispulse output would then'be applied as described above to the keyer pulseinput of pick-up unit 3.

Fig. 5 indicates a further system wherein a sawtooth generator "108 "isactivated by signals from the sync generator. The sawtooth coupledtherefrom has a time base equivalent -to the time of the scanning heldwith a peak voltage of a su'itable 'value. This sawtooth is then presented to the diode type electron discharge device 109, the circuitrythereof being arranged to conduct at time zero and will cut ed at aparticular time, as established by the variable bias 1143 applied to thecathode of the diode 109. The resultant keying pulse 111, therefore, mayhave its leading edge-112 varied in time'dependent upon the bias appliedto diode 169 and at .the same time will control the amplitude'of thepulse'lll, as will be apparent to those skilled in the art. This keyingpulse will likewise be applied as described above to .the' keyer pulseinput of pick-'up' unit' 3. a a

This basic system "and principle may be extended to handle more than twovideo signals for simultaneous presentation in a TV frame by increasingthe number of montage amplifierchannels and by producing a keying pulseto aid in the required simultaneous presentation,

both changes requiring an expansion of the present e'lectrical andmechanical apparatus. As hereinabove described, it is possible totransmit more than two video signals at a time in one signal frame byoverlapping two picture signals and fade one signal out partially whilebringing a third and possibly a fourth picture signal up to brightness,preseutingthree and possibly four picture signals simultaneously on onesignal frame.

While I have described .above the principles of my invention inconnection with specific apparatus, it is to be clearly understood thatthis description ismade by way of example only and not as a limitationto the scope of my invention as set forth in the objects thereof and inthe accompanyingclaims.

I claim: a

1. In a television system, at least three video signal sources, anamplifier circuit including two signal amplifying channels for combiningcertain frame portions of the signals ofselected ones of said videosignal sources for transmission in thesamesignal frame, channeling meansfor applying signals of said selected sources selectively-to saidamplifying channels, means for producing control signals in accordancewith a desired division of said signal frame, andselective means forapplying said icontrol signals directly to each of said amplifyingchannels for controlling conduction -ofsignals of said selected sourcestherethrough according to said frame division, said channeling means forapplying signals comprising switching means, mixing means, and means formanually controlling the video level of said video signal sources priorto presentation'to-said mixing'means, said switching means beingarrangedfor selection of signals from said video signal sources forconduction'through said mixing means for application selectively to saidamplifying channels, said switching means comprising a plurality ofpushbuttons for selection for a particular one of said amplifyingchannels, one of said pushbuttons providing establishment ofsubstantially equal bias on said channels for manual control of selectedvideo signals for a superimposition, lap dissolve, or fade outpresentation in said signal frame, a fade rate switch and an auto switchcoupled between said pushbuttons and said amplifying channels includingmeans having a double RC time constant providing three different ratesof interchange when changing from one channel to the other channel ofsaid amplifier circuit by actuation of said pushbuttons.

2. In a television system according to claim 1, further including anormal-montage switch to provide selection of video signals to bepresented to a particular channel of said amplifier circuit and toprovide an automatic time sharing of said signal frame by selected videosignals, and double throw switches coupled between said video signalsources and said mixing means cooperating in selecting the channel ofsaid amplifier circuit through which selected video signals may beconducted.

3. In a television system according to claim 2, wherein said mixingmeans includes eight cathode followers in groups of four, the cathodesof said groups being connected in parallel and coupled to theirrespective channel of said amplifier circuit, the input to said groupsbeing coupled by the proper throw of said double throw switches to therespective grids of said cathode followers.

4. In a television system, a plurality of video signal sources, anamplifier circuit for combining certain frame portions of the signals ofselected ones of said video signal sources for transmission in the samesignal frame, channeling means for applying signals of selected sourcesto said amplifier circuit, means for producing control signals inaccordance with a desired division of said signal frame, and selectivemeans for applying said controlling signals directly to said amplifierfor controlling conduction of signals of said selected sources accordingto said frame division, said channeling means comprising switchingmeans, mixing means and means for manually controlling the video levelof said video signal source prior to presentation to said mixing means,said switching means being arranged for selection of signals from saidvideo signal source for conduction through said mixing means forapplication to said amplifier circuit, said switching means comprising aplurality of pushbuttons for selection for a particular portion of saidamplifier circuit, one of said pushbuttons providing establishment ofsubstantially equal bias on said portions for manual control of selectedvideo signals for a superimposition, lap dissolve, or fade outpresentation in said signal frame, a fade rate switch and an auto switchcoupled between said pushbuttons and said amplifier circuit includingmeans having a double RC time constant providing three difierent ratesof interchange when changing from one portion to the other portion ofsaid amplifier circuit by actuation of said pushbuttons.

5 In a television system according to claim 4, further including anormal-montage switch to provide selection of video signals to bepresented to a particular portion of said amplifier circuit and toprovide an automatic time sharing of said signal frame by selected videosignals, and double throw switches coupled between said video signalsources and said mixing means cooperating in selecting the portion ofsaid amplifier circuit through which selected video signals may beconducted.

6. In a television system according to claim 5, wherein said mixingmeans includes eight cathode followers in groups of four, the cathodesof said groups being connected in parallel and coupled to theirrespective portion of said amplifier circuit, the input to said groupsbeing coupled by the proper throw of said double throw switches to therespective grids of said cathode followers.

References Cited in the file of this patent UNITED STATES PATENTS2,164,297 Bedford June 27, 1939 2,193,869 Goldsmith Mar. 18, 19402,240,420 Schnitzer Apr. 29, 1941 2,490,561 Ussler Dec. 6, 19492,510,714 Patremio June 6, 1950 2,546,338 Glasford et al Mar. 27, 19512,611,819 Serrell Sept. 23, 1952 2,613,263 Hilburn Oct. 7, 19522,653,186 Hurford Sept. 22, 1953 2,697,746 Kennedy Dec. 21, 1954

